Miniature Heat Air Conditioning?

Hello,
I am purchasing a new pet corn snake and was wanting to build my own vivarium/cage for him/her. i want it to be about 38 gallons and it will have plexiglass sliding and locking doors. My first question is does anyone have any idea on any possibilities of a small in tank heater/air conditioning. this is because during summer i work on nature staff at camp raven knob N.C. and my cabin does not have AC (and my houses sux) and during the winter it gets very cold here and since i live in an old house the insulative properties arent great. Is this a plausible idea? kind of like a miniature window air conditioner for a tank? Also any free vivarium plan sites are appreciated.
Thank You

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